Locally Produced Inflammatory Cytokines in Human Chronic Adult Periodontitis. Adult periodontitis is a chronic inflammatory disease involving breakdown of supporting structures of the teeth. The interaction between virulence factors of microbial pathogens in dental plaque and the host immune response is a major inducer of the disease. Many inflammatory cytokines have been implicated in the disease process, although direct evidence is presently limited. In our recent studies, inflamed periodontal tissue and crevicular fluid (CF) from periodontitis patients were collected and analyzed for the presence of cytokines. The CF was assayed for both IL-1 and IL-1 receptor antagonist (IL-1ra) by ELISA. Gingival tissue was processed for assessing the presence of cytokine mRNA, or gingival mononuclear cells (GMNC) were isolated for FACS analysis of surface markers. The cytokine mRNA was reversed transcribed and amplified by the polymerase chain reaction (RT-PCR). Human blood mononuclear cells activated with lipopolysaccharide and phytohemagglutinin served as positive controls, with sterile water serving as the RT- PCR negative control. FACS analysis showed that GMNC samples with a high B/T cell ratio had more CD4+ than CD8+ cells, while those with a high T/B ratio had more CD8+ than CD4+ cells. GMNC with a high B/T ratio had lower percent of cells staining for IL-1 receptor and IL-8 receptor than GMNC with a high T/B ratio. CF containing low levels of IL-1 had high levels of IL-1ra. Analysis of tissue mRNA revealed message for cytokines IL-1, TNF-alpha, IL-6, and IL-8. These results indicate an ongoing cellular and cytokine regulation in chronically inflamed tissue of adult periodontitis patients. Ph.D. Microbiology with clinical special in Periodontics.